Frequently the case with HDFCs - or low-income or median-income affordable coops - is such that the price is too low for most financial institutions to consider it a mortgage. At UHAB, we work for free to sell affordable coops to qualified buyers who have enough to pay a downpayment and the maintenance and mortgage.
The credit unions and small banks we work with sort of set up loans instead of mortgages in some cases, because the "mortgage" would effectively wind up being about $30,000 or so.
Check out our site - the Urban Homesteading Assistance Board - for more information. http://www.uhab.coop